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Lapping an Obsidian

In the spirit of experimentation I got a few more random stones to try them out as hone.
So far, my best luck have been with Agate and Jade. Synthetic ruby has been working great too.
For Onyx, I am still working out the impact of impurity.

Anyway, I found a large flat black obsidian. Well, flat and lapped are almost the same thing, but not quite.
So far I have spent quite some time working it on the Norton lapping stone, and I am wondering if I am lapping my lapping stone. That thing is HARD.

$Rainbow Sheen Obsidian Davis CK CA.jpg

As anybody tried?
 
Have you given SiC powder a try? It makes pretty short work of an Arkie and they're harder even than obsidian. While it seems there's variation, the listed hardness on the Mohs scale for Obsidian is 5.5 and for Arkies it's around 7. You could probably get away with using 600 or 800 grit SiC on that.

Love looking at the stones you use to hone. It's very cool.
 
Be careful - obsidian can cleave easily enough and the resulting fracture can leave an edge that will make your best edge look like it's duller than a bread knife. If it snaps - let it fall or you can get cut reallllllly bad.

I don't think you'll get much from the Obsidian as a hone, but it could be interesting.
Consider trying a piece of Hematite next time around.
 
It is volcanic glass. Does it have grit? I would expect more of a burnishing/polishing effect.

Purely speculation though.
Once you get past 12K or so, it is pretty much just polishing anyway.
I have some Agate that gives me finer scratches than crOx. Way beyond my Shapton 16K.
I now get HHT of the stone, with on my hair never happened even after 16K (0.9 microns).
 
I don't think you'll get much from the Obsidian as a hone, but it could be interesting.
Consider trying a piece of Hematite next time around.
Feeling the stone surface, I have the same impression. I'll give it a try anyway since I have it, but on a cheap razor.
 
Its alleged that Obsidian will cleave and create an edge with an EW that is 1-molecule wide.
Or something like that. I've chipped it and gotten hurt, shard stuck in my finger. Scary sharp stuff.
 
Its alleged that Obsidian will cleave and create an edge with an EW that is 1-molecule wide.
Or something like that. I've chipped it and gotten hurt, shard stuck in my finger. Scary sharp stuff.
Now I am intrigued.
I am definitely trying it...
 
Online, somewhere - there's a paper on sharpening that references why steel can't ever be as sharp as obsidian.
I remember it was a good read, but can't remember the specificis.
 
Online, somewhere - there's a paper on sharpening that references why steel can't ever be as sharp as obsidian.
I remember it was a good read, but can't remember the specificis.
Something about the crystalline nature of steel vs the noncrystalline glass I think.
 

SliceOfLife

Contributor
I'd assume it's because martensitic steel can't be one molecule wide, so if you ever got steel that refined, it'd be too soft to actually use at the edge. But I'm no metallurgist.
 
Consider trying a piece of Hematite next time around.
So I looked those up. It seems to be close to carborundum in composition. What stage of honing do you think this would work for?
Isn't carborundum what barber's hone are made of?
 
Carborundum is Silicon Carbide (SIC) - Hemetite is an Iron Oxide.

Setting Razors. Part 3

The Charnley Forest stone is generally preferred for the first stage or for striking off the wiry edge of the blade. The Turkey oilstone is sometimes used for the same purpose. The Green hone or Welsh hone, which is harder than the Charnley Forest, and generally in smaller pieces, is occasionally used for razors, and is by some preferred to Charnley Forest for finishing pen and pocket knives, and especially for setting surgeons' instruments.
The yellow German hone, particularly the slabs from the lower strata known as old rock, is greatly preferred to all the above for the principal office in setting razors, as it cuts more slowly, smoothly, and softly, than any of them. The Iron stone or slabs of the hematite iron ore, are occasionally used for giving the final edge, it consists principally of oxide of iron, and chemically resembles crocus, but that it is in a compact, instead of a disintegrated form. The iron stone is however so very hard that it appears to act more as a burnisher than a hone, and renders the edge almost too smooth, so that when at all used, the razor is in general only passed once or at most twice on each side along the iron stone.
 
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